Abstract

Rockfall is an important natural hazard in steep alpine areas, in particular in the areas adjacent to shrinking glaciers. However, the process is difficult to assess as rockfall intensity is governed by several factors, which vary in time and space. This study aims to quantify small
magnitude rockfall processes in a high mountain catchment (1800–3559 m) affected by rapid deglaciation. In order to quantify current rockfall processes, low magnitude rockfalls (< 10 m3) are registered by collector nets and in natural sediment traps. The determined rockfall
intensities range over four orders of magnitude (0.016–138 g/m2/d – corresponding to a rockwall back-weathering rate of 0.0022–18.6 mm/a). The results suggest that rockfall intensity is mainly governed by the temporal onset of the deglaciation of the rock face
and by rock mass properties. The recent deglaciated rock slopes show on average at least two orders of magnitude higher rockfall intensity than the rock slopes that have been ice-free since the late Pleistocene deglaciation. The highest rockfall intensities are attributed to weak rock masses
characterized by extremely fractured bedrock along a major fault.